A tremendous variety of token-actuated devices are known and have proved commercially successful, including (but not limited to) parking meters which control individual parking spaces, vending machines, newspaper racks, electronic games, and jukeboxes. Many token-actuated devices respond to the insertion of a token which is legal tender (that is, a coin). Other token-actuated devices respond to a token which is not itself legal tender and which is ordinarily specifically designed for use in a particular type of token-actuated device. (As used herein the term "token" includes both a token which is legal tender in some nation and a specially-designed token which is not legal tender.)
Many early token-actuated devices were wholly mechanical. Examples of such devices are early parking meters, such as those disclosed in U.S. Pat. No. 1,799,056 to Miller and U.S. Pat. No. 2,603,288 to Sollenberger.
Although mechanical token-actuated devices remain useful, mechanical devices have disadvantages in comparison with electronic devices. Mechanical devices generally have many more moving parts than electronic devices; those moving parts tend to need repair or replacement more frequently than electronic parts. Replacing mechanical parts ordinarily requires much more labor than replacing electronic parts.
Electronic devices have other advantages in comparison with mechanical devices. For example, electronic devices can economically provide a wide variety of special functions which would be prohibitively expensive to implement in a wholly mechanical device.
Thus, those working in the field of token-actuated devices have sought to develop token-actuated devices which incorporate electronic components. See, for example, U.S. Pat. Noa. 3,757,916 to Selby; 4,031,991 to Malott; 4,792,032 to Shapiro; 4,848,556 to Shah, Pester, and Stern; and 4,823,928 to Speas.
One problem which has impeded the wider use of electronic token-actuated devices is the amount of current which an electronic token-actuated device draws in its operation. Many types of token-actuated devices --particularly parking meters and newspaper racks--are ordinarily used in places where the devices cannot be conveniently connected to electric power lines. Thus, those types of token-actuated devices must usually rely on batteries for electric power. (U.S. Pat. No. 4,823,928 to Speas also discloses the use of solar cells.) Because a battery can only supply a limited amount of current before the battery must be recharged and/or replaced, a battery-powered token-actuated device should draw as little current as possible.
The requirement for low current consumption has limited the ability of battery-powered token-actuated devices--such as parking meters--to perform certain desirable functions. Thus, there has been and is a need to develop improved designs so that electronic token-actuated devices can perform desired functions with low current consumption.
One function which electronic token-actuated devices can perform, and which mechanical token-actuated devices can perform (if at all) only at great cost and inconvenience, is to provide a signal which indicates the number of tokens and (if the tokens are legal tender) the amount of money contained in a token vault or other receptacle attached to the token-actuated device. Such signals assist a central authority (such as the parking division of a city) in checking to make sure that all money received by token-actuated devices has actually been returned to the central authority by the personnel assigned to collect the money from the token-actuated devices. In addition, an electronic token-actuated device (such as an electronic parking meter) can store and later transfer other types of detailed information about usage of the token-actuated device. Such other information may include, in the case of a parking meter, the time of day at which the parking meter was used and the length of time for which the parking meter was used at the time when it was used. Such information can be very useful to the parking and traffic authorities of a city in determining what fare structure to implement for a series of parking meters and in learning when peak usage periods occur.
As the application of electronic technology to token-actuated devices has become more advanced, token-actuated devices have been designed including advanced electronic components such as programmable microprocessors and potentially considerable amounts of memory to hold a stored program to control the microprocessor and also to hold data which may later be collected from the microprocessor. The conventional way of changing the program for the microprocessor has been to replace one read-only memory chip containing one program with another read-only memory chip containing another program. Alternatively, some token-actuated devices (such as the parking meter sold under the registered trademark "EPM" by Duncan Industries Parking Control Systems Corp.) have incorporated a data interface connected to a wire connector. The token-actuated device sends data to, or receives data from, such a data interface when someone (such as a parking meter attendant assigned to collect money from parking meters) attaches a cable to the wire connector and, using a hand-held device, receives data from, or sends data to, the electronic components inside the parking meter.
Such a wire connector has several disadvantages. First, it presents an additional opening through which the elements may potentially enter the interior of a token-actuated device. This disadvantage is particularly severe for token-actuated devices (such as parking meters) located outdoors, Second, wire connectors offer some possibility for vandals to seek to tamper with a token-actuated device (such as by attaching a battery and attempting to confuse, or to interfere with the operation of, the device). Third, a wire connector requires that an attendant go through the step of connecting a wire to the wire connector. Such a step can be inefficient. For example, if there are no tokens to be removed from the token-actuated device (or if the value of the tokens in the token-actuated device is too low to make a collection stop worthwhile), it can be inefficient for an attendant to go over to the token-actuated device, connect a wire to the wire connector, and then learn that there are no tokens to collect (or not enough tokens to collect to make the stop worthwhile).
Those designing token-actuated devices have thus turned to infrared communications to dispense with the wire connectors. Infrared communications can occur through a transparent cover, which most token-actuated devices (especially parking meters) already have; this eliminates the need for an opening for a wire connector. Vandals are somewhat less likely to carry infrared communications devices than to carry tools or batteries which could be used to try to interfere with the operation of an electronic device through a wire connector. An attendant can operate an infrared communications device faster than a device which requires attachment to a wire connector on a token-actuated device. Moreover, considerable disclosure exists describing the use of infrared communications in outdoor environments--particularly as applied to utility meters.
A major difference between many token-actuated devices and utility meters is that many token-actuated devices are located away from conventional electric power lines and thus must draw their electric power from batteries (or in some instances from solar cells, such as disclosed in U.S. Pat. No. 4,823,928 to Speas). The need to rely on batteries creates a need for an infrared communications circuit to draw as little current as possible when installed in such a token-actuated device.
Conventional infrared communications circuits have the disadvantage of drawing more current than is convenient for use in a battery-powered token-actuated device. Drawing too much current reduces the lifetime of the batteries used in such a token-actuated device and thus requires more frequent replacement of the batteries. Those problems in turn reduce the efficiency of using an electronic token-actuated device and create problems of inaccurate operation of the token-actuated device when the battery runs down.
In addition, an infrared communications circuit in a token-actuated device should be able not only to send but also to receive data. It may be desirable to send data to an electronic token-actuated device to change the operating program of the device. For example, in the illustrative case of a parking meter, it may be desirable to change the amount of time allotted for a given coin or coins or to program the parking meter to switch to a maximum revenue production mode where time is erased if additional purchase is attempted after a given time interval.
Because such communication to an electronic token-actuated device can occur at any time, an infrared communications receiver in an electronic token-actuated device must be continuously able to receive communications from an authorized source. This need for continuous readiness to receive communications makes conventional infrared communications circuits even more unsuitable; such conventional infrared communications circuits draw too much current to begin with, and yet they must be ready to receive infrared communications at any time.
Moreover, environments where token-actuated devices are located may contain a wide variety of infrared light sources within the frequencies to which the infrared detector in the infrared communications circuit may respond. It is important generally that such infrared light sources not be incorrectly perceived as new data by the token-actuated device. Moreover, even if such infrared light sources are not incorrectly perceived as data, it is also important that such infrared light sources not cause the parking meter to draw current wastefully.
Finally, an infrared communications circuit in a token-actuated device must robustly resist signals from such widely-available infrared communications devices as hand-held infrared communications devices designed for use with television channel changing circuits or for use with other home entertainment devices such as compact disk players.
Thus, there has been and is a need for an improved infrared communications circuit for use in an electronic token-actuated device which remains continuously ready for receiving and sending data and has one or both of the characteristics of drawing very little power even in the presence of environmental sources of infrared light (particularly in an outdoor environment) and resisting influence from infrared communications devices intended for use with other machines.